Help needed on HP 7900A disk drive (mechanical)

From: Jay West <jlwest_at_tseinc.com>
Date: Thu Jun 17 19:24:16 1999

I'm in need of sage advice from others on the list, due to my lack of
troubleshooting/repair experience with large (14") hard drives. I'm a
sophomore with electronics, but these beasties are largely mechanical and
out of my meager knowledge set.

Background:
I finally got a brand new (yes, really brand new) blank disk cartridge for
my HP 7900A disk drive. The drive has never been powered up since I got it.
The spindle motor won't even start on these drives unless the cartridge is
in place (there is also a fixed platter underneath). Since the drive is
obviously not checked out, I wanted to get blank media to test so I didn't
ruin valuable data on a cartridge I am getting later. First I very
thoroughly cleaned the drive inside and out, cleaned all contacts, heads,
positioner reticule, etc. etc. etc. I then checked the power supply out
carefully. Then I powered up the drive (without the cartridge) and tested a
number of the basic mechanical functions, interlocks, and test points on
some of the cards called out by the operating manual. Then I wanted to try
loading the cartridge to see if the heads would crash nicely :) Keep in mind
that once the cartridge is in, there is a load switch that powers up the
spindle and 30 seconds later the heads do a seek. At any time during the
spin up or seek, the unload switch will immediately and very quickly retract
the heads and then the drive spins down.

"Problem":
I put the cartridge in the drive and hit load. You can hear the spindle come
up to speed. Exactly 30 seconds later as stated in the operators guide, you
can hear the heads move and then the drive ready light comes on. From what I
understand if there are any problems at all up to this point, the drive
fault lite would come on (including a seek fail, etc.). I kept my finger on
the unload switch. The second the heads came out I could hear a
disconcerting noise. I immediately hit unload. I removed the cartridge, and
inspected both the cartridge and heads carefully. No obvious signs of
problems. I reloaded the cartridge. This time, when drive ready lit up, the
drive was nice and quiet for about 25 seconds. Then I started hearing the
noise again. On and off, more and more, so I hit unload. Rechecked the heads
and cartridge again - no obvious signs of damage. Tried loading the
cartridge again. This time it ran for a few minutes before I heard the
noise. I unloaded and rechecked everything, still no signs of problems.
Gee - can you tell I'm paranoid about possibly ruining the new cartridge
and/or the heads? :)

The sound is not quite metallic, but very close. It sounds like something
rubbing at high speed but at a pretty high pitch. The best way I can
describe it is that it is almost identical to the sound an 8" floppy disk
makes when you put it into an RX02 drive and close the door (the media
turning inside the sleeve), but much louder. I'm pretty uncomfortable
proceding with diagnostics, etc. unless someone here can calm my fears as to
what the sound might be. Is it just due to the fact that it's a brand new
cartridge, or is it indicative of a potential head crash, just a belt issue,
dust, etc? I'm pretty familiar with the whine a drive makes when the
bearings are going out, and it does not sound like that sound.

Any help, ideas, thoughts, etc. are MOST appreciated!

Jay West
Received on Thu Jun 17 1999 - 19:24:16 BST